Re: [PATCH] cfq-prio #2

[Nick Piggin]

Jens Axboe wrote:

> On Tue, Nov 11 2003, Nick Piggin wrote:
>
> > You acked the change actually :P
> > I guess it was done in mainline when AS was merged.
>
> Probably missed the semantic change of may_queue.

Anyway I won't bother digging up the email, its been done now.

> > > > Maybe my version should be called elv_force_queue?
> > > I just hate to see more of these, really. The original idea for
> > > may_queue was just that, may this process queue io or not. We can make
> > > it return something else, though, to indicate whether the process must
> > > be able to queue. Is it really needed?
> > Its quite important. If the queue is full, and AS is waiting for a process
> > to submit a request, its got a long wait.
> >
> > Maybe a lower limit for per process nr_requests. Ie. you may queue if this
> > queue has less than 128 requests _or_ you have less than 8 requests
> > outstanding. This would solve my problem. It would also give you a much more
> > appropriate scaling for server workloads, I think. Still, thats quite a
> > change in behaviour (simple to code though).
>
> That basically belongs inside your may_queue for the io scheduler, imo.

You can force it to disallow the request, but you can't force it to allow
one (depending on a successful memory allocation, of course).


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